As magnetic recording is pushed to higher areal densities, perpendicular recording may offer advantages in thermal stability over longitudinal recording, thus delaying arrival at the super-paramagnetic limit [1,2]. Another advantage of perpendicular recording with single pole (SP) head and perpendicular media, with a soft underlayer (SUL), is the ability to produce a larger write field than that of a ring head to record on relatively thick media with high anisotropy constant. Although these assumed advantages indicate that perpendicular recording has high recording density potential, perpendicular recording does not, thus far, surpass the highest recording density achieved using thermally stable AFC media [3]. This is the result of the insufficient field gradients produced by a perpendicular SP head in both the cross-track and down-track directions, thus limiting the achievable recording density.
Introduction of a downstream shield, extending from the return pole, has been proposed to increase the trailing edge field gradient as well as the in-plane head field component [4,5]. An example of this is shown in FIG. 1. Magnetic yoke 11 is surrounded by field coil 12 and includes pole tip 13. Introduction of a downstream shield, extending from the return pole, has been proposed to increase the trailing edge field gradient as well as the in-plane head field component [4,5]. An example of this is shown in FIG. 1. Magnetic yoke 11 is surrounded by the coil 12 and includes pole tip 13. Without an extended return pole, total magnetic flux generated by coil 12 is conducted from main pole 13 into soft underlayer 16 with a certain spread width in the down-track direction, and eventually collected by the return pole 14 to complete the magnetic circuit. As shown in FIG. 1, the extended return pole 15 intercepts partial magnetic flux from the main pole. Thus, the field spread width is reduced, i.e. field gradient is increased.
However, extending return pole 14 as far as the vicinity of main pole 13 introduces a large undershoot perpendicular field at the trailing edge, similar to the case of a longitudinal ring head, and also reduces the maximum field in the recording media. The present invention discloses how this problem may be overcome.